2 files changed, 216 insertions, 0 deletions
diff --git a/pkg/storage/index/index.go b/pkg/storage/index/index.go
new file mode 100644
index 0000000..ef9ad60
--- /dev/null
+++ b/pkg/storage/index/index.go
@@ -0,0 +1,103 @@
+// Package index provides an index of locally stored certificates.  If a method
+// succeeds, the index and the data that it tracks has been persisted to disk.
+// If a method does not succeed, restore from the persisted index on disk.
+package index
+
+import (
+	"crypto/sha256"
+	"fmt"
+	"time"
+
+	"rgdd.se/silent-ct/internal/ioutil"
+	"rgdd.se/silent-ct/internal/monitor"
+	"rgdd.se/silent-ct/pkg/crtutil"
+)
+
+type Config struct {
+	PermitBootstrap bool   // Create a new index if a valid one does not exist on disk yet
+	IndexFile       string // Path to an index file that can be read/written
+	TrustDirectory  string // Absolute path to an existing directory where legitimate certificates are stored
+	MatchDirectory  string // Absolute path to an existing directory where matching certificates are stored
+
+	// Optional
+	AlertDelay time.Duration // Time before alerting on certificates that are unaccounted for
+}
+
+type Index struct {
+	mem index
+	cfg Config
+}
+
+func New(cfg Config) (Index, error) {
+	ix := Index{cfg: cfg}
+	if err := ioutil.DirectoriesExist([]string{cfg.TrustDirectory, cfg.MatchDirectory}); err != nil {
+		return Index{}, err
+	}
+	if err := ioutil.ReadJSON(cfg.IndexFile, &ix.mem); err != nil {
+		if !cfg.PermitBootstrap {
+			return Index{}, err
+		}
+
+		ix.mem = newIndex()
+		if err := ioutil.CommitJSON(cfg.IndexFile, ix.mem); err != nil {
+			return Index{}, err
+		}
+	}
+	return ix, ix.Validate()
+}
+
+func (ix *Index) AddChain(node string, pem []byte) error {
+	chain, err := crtutil.CertificateChainFromPEM(pem)
+	if err != nil {
+		return err
+	}
+
+	var crtID CertificateID
+	crtID.Set(chain[0])
+	path := fmt.Sprintf("%s/%s-%s.pem", ix.cfg.TrustDirectory, node, crtID)
+	if !ix.mem.addChain(crtID, path) {
+		return nil // duplicate
+	}
+
+	if ioutil.CommitData(path, pem); err != nil {
+		return err
+	}
+	return ioutil.CommitJSON(ix.cfg.IndexFile, ix.mem)
+}
+
+func (ix *Index) AddEntries(logID [sha256.Size]byte, entries []monitor.LogEntry) error {
+	addEntry := func(entry monitor.LogEntry) error {
+		crt, err := crtutil.CertificateFromLogEntry(entry.LeafData, entry.ExtraData)
+		if err != nil {
+			return err
+		}
+
+		var crtID CertificateID
+		crtID.Set(crt)
+		path := fmt.Sprintf("%s/%x-%d.json", ix.cfg.MatchDirectory, logID[:], entry.LeafIndex)
+		if !ix.mem.addEntry(crtID, path) {
+			return nil // duplicate
+		}
+
+		return ioutil.CommitJSON(path, entry)
+	}
+
+	for _, entry := range entries {
+		if err := addEntry(entry); err != nil {
+			return err
+		}
+	}
+	return ioutil.CommitJSON(ix.cfg.IndexFile, ix.mem)
+}
+
+func (ix *Index) TriggerAlerts() ([]CertificateInfo, error) {
+	alerts := ix.mem.triggerAlerts(ix.cfg.AlertDelay)
+	if len(alerts) == 0 {
+		return []CertificateInfo{}, nil
+	}
+	return alerts, ioutil.CommitJSON(ix.cfg.IndexFile, ix.mem)
+}
+
+func (index *Index) Validate() error {
+	return nil // FIXME: check that the index is populated with valid values
+}
diff --git a/pkg/storage/index/inmem.go b/pkg/storage/index/inmem.go
new file mode 100644
index 0000000..0a084bf
--- /dev/null
+++ b/pkg/storage/index/inmem.go
@@ -0,0 +1,113 @@
+package index
+
+import (
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"github.com/google/certificate-transparency-go/x509"
+	"rgdd.se/silent-ct/pkg/crtutil"
+)
+
+type CertificateID string
+
+func (crtID *CertificateID) Set(crt x509.Certificate) {
+	*crtID = CertificateID(crtutil.UniqueID(crt))
+}
+
+type CertificateInfo struct {
+	ObservedAt time.Time `json:"observed_at"`
+	StoredAt   string    `json:"stored_at"`
+}
+
+// index is an in-memory index of certificates
+type index struct {
+	Alerting   map[CertificateID][]CertificateInfo `json:"alerting"`   // Certificates that were not marked as "good" on time
+	Legitimate map[CertificateID][]CertificateInfo `json:"legitimate"` // Certificates that are considered "good"
+	Pending    map[CertificateID][]CertificateInfo `json:"pending"`    // Certificates that have yet to be marked as "good"
+}
+
+func newIndex() index {
+	return index{
+		Alerting:   make(map[CertificateID][]CertificateInfo),
+		Legitimate: make(map[CertificateID][]CertificateInfo),
+		Pending:    make(map[CertificateID][]CertificateInfo),
+	}
+}
+
+func (ix *index) JSONUnmarshal(b []byte) error {
+	type internal index
+	if err := json.Unmarshal(b, (*internal)(ix)); err != nil {
+		return err
+	}
+	for i, m := range []map[CertificateID][]CertificateInfo{ix.Alerting, ix.Legitimate, ix.Pending} {
+		if m == nil {
+			return fmt.Errorf("dictionary named %q is not in the index", []string{"alerting", "legitimate", "pending"}[i])
+		}
+	}
+	return nil
+}
+
+func (ix *index) triggerAlerts(delay time.Duration) []CertificateInfo {
+	var alerts []CertificateInfo
+
+	for key, certInfos := range ix.Pending {
+		certInfo := certInfos[0]
+		if time.Since(certInfo.ObservedAt) < delay {
+			continue
+		}
+
+		alerts = append(alerts, certInfo)
+		ix.Alerting[key] = certInfos
+		delete(ix.Pending, key)
+	}
+
+	return alerts
+}
+
+func (ix *index) addChain(crtID CertificateID, path string) bool {
+	if _, ok := ix.Legitimate[crtID]; ok {
+		return false // we already marked this certificate as "good"
+	}
+
+	entry := CertificateInfo{ObservedAt: time.Now(), StoredAt: path}
+	crtInfos := []CertificateInfo{entry}
+	if v, ok := ix.Alerting[crtID]; ok {
+		crtInfos = append(crtInfos, v...)
+		delete(ix.Alerting, crtID) // no longer alerting
+	} else if v, ok := ix.Pending[crtID]; ok {
+		crtInfos = append(crtInfos, v...)
+		delete(ix.Pending, crtID) // no longer pending
+	}
+
+	ix.Legitimate[crtID] = crtInfos
+	return true // index updated such that this certificate is marked as "good"
+}
+
+func (ix *index) addEntry(crtID CertificateID, path string) bool {
+	crtInfo := CertificateInfo{ObservedAt: time.Now(), StoredAt: path}
+	if _, ok := ix.Legitimate[crtID]; ok {
+		return add(ix.Legitimate, crtID, crtInfo)
+	} else if _, ok := ix.Alerting[crtID]; ok {
+		return add(ix.Alerting, crtID, crtInfo)
+	}
+	return add(ix.Pending, crtID, crtInfo)
+}
+
+func add(m map[CertificateID][]CertificateInfo, key CertificateID, value CertificateInfo) bool {
+	crtInfos, ok := m[key]
+	if !ok {
+		m[key] = []CertificateInfo{value}
+		return true
+	}
+
+	for _, crtInfo := range crtInfos {
+		if value.StoredAt == crtInfo.StoredAt {
+			return false // duplicate
+		}
+	}
+
+	crtInfos = append(crtInfos, value)
+	m[key] = crtInfos
+	return true
+}